So I did a test on both my tank water and my tap water before I left. Turns out my tap water reads ammonia at .5 so every time I changed my water I was adding ammonia to the tank!
Fortunately my bb is keeping it in check causes tank is at 0 ppm.
But now what do I do. How can I change the water safely?

If your tank has a stable cycle and/or lots of live plants (I'm assuming you do since you say your BB takes care of it), all you really need to do is use a conditioner that will detoxify the ammonia long enough for the bacteria to take care of it. The only conditioner that I know of that does this is Prime, but there may be others.

If your tank has a stable cycle and/or lots of live plants (I'm assuming you do since you say your BB takes care of it), all you really need to do is use a conditioner that will detoxify the ammonia long enough for the bacteria to take care of it. The only conditioner that I know of that does this is Prime, but there may be others.

Kordon Ammonia Detoxifier (aka AmQuel Plus) is another popular one, and the one I use.

The only reason I think the bb is taking care of it is because I did a water change yesterday with the .50 ppm while my water in the tank was at a .25 ppm and today it's at 0 ppm. But prime and kordon?

prime chemically binds to the ammonia and turns it into ammonium. prime does show up initially as ammonia in a test kit. this,however dissipates in about 24 hrs.the test kits cannot differentiate between ammonium and ammonia. i am not sure if kordon works the same way. i have no experience with it. i just recently learned to not use prime with coppersafe ich treatment. the chemical reaction can poison aquatic life. just fiy. i am treating for velvet and have to use spring water.

FYI someone pointed me to a seachem ammonia alert device that sticks on inside of tank. Seems to work well. I have some ammonia in my tap water (.25) and this helps me keep an eye on it. I use prime, but the alert device only shows the harmful ammonia (the api master test kit apparently doesn't differentiate.)